CD4 and dengue disease: Using EA.hy926 cells and HUVEC cells, we have demonstrated that (i) severe dengue plasma-derived EV (SD-EV)-treated CD4+ T cells have retarded proliferation and impaired the migratory ability of endothelial cell (EC); (ii) SD-EV-CD4+ T cell induces PD-L1 expression on endothelial cells.